The invention concerns a gear pump capable of pumping high viscosity media from a relatively low pressure against a relatively high pressure. This invention also concerns pump installations with such a gear pump as well as the use of this gear pump, especially for discharging high viscosity media from a vacuum against a high pressure.
In the past, when pumping a highly viscous medium from a vacuum or an area of low pressure against a high pressure the medium being pumped had a tendency to boil or form gases. This in turn led to cavitations in the pump which drastically reduced its capacity. To prevent the development of gas and cavitation, it is necessary to increase the inlet pressure to a suitably high level by increasing the static pressure of the liquid column above it. Cavitation in the pump must be avoided at all costs because it not only causes the output of the pump to stop, it also damages the pump itself. To achieve a good pumping capacity, the inlet area of known gear pumps has been designed in such a way that the medium is fed directly to the gears. Such a pump is known from U.S. Pat. No. 4,137,023.